The scenario describes a mismatch in OSPF network types between two connected routers: one set to Point-to-Point (P2P) and the other set to Point-to-Multipoint (P2MP). While aligning Hello intervals may seem sufficient for establishing an OSPF neighbor relationship, the fundamental mismatch in network types introduces issues.
OSPF Network Types
P2P: Assumes a direct connection with a single neighbor, uses faster convergence and simpler LSDB synchronization.
P2MP: Supports multiple neighbors on a single interface, requiring different handling for DR/BDR roles and LSDB updates.
Impact of Network Type Mismatch
If Hello intervals are aligned, adjacency establishment might occur. However, mismatched network types affect neighbor role assignment and LSDB synchronization.
P2P expects a direct link and would handle updates differently than P2MP, which assumes multiple neighbors. This leads to inconsistencies in route calculation and forwarding.
HCIP-Datacom-Core Reference
OSPF Basics and Configuration​clearly outlines the criticality of consistent network type configuration for stable OSPF operation.
Lab examples in the HCIP Datacom Lab Guide​further demonstrate the consequences of such mismatches, including unstable neighbor states and incomplete LSDB synchronization.
Hence, the statement that neighbor relationships and LSDB synchronization remain unaffected is incorrect. Proper OSPF operation requires matching network types in addition to aligned Hello intervals.
